Separation using cyclodextrin

Electrophoretic ally Driven Preparative Chiral Separations using Cyclodextrins... 

Rawjee, Y.Y., Williams, R.L., Vigh, G. Capillary electrophoretic chiral separations using cyclodextrin additives III. Peak resolution surfaces for ihuprofen and homatropine as a function of the pH and the concentration of fS-cyclodextrin. J. Chromatogr. 1994, 680, 599-611. 

In the recent past separation of isomers has been attempted using aqueous liquid membranes based on p-cyclodextrin. Thus, separation of a mixture of o- and p-nitroaniline (in 80% i-octanol, 20% -heptane) has been studied, with the p-isomer showing a selectivity of 5 at 0.7 molar p-cyclodextrin. Even stereoisomers of stilbene cis and trans) were separated using a 0.02 to 0.2 M cyclodextrin solution, but the selectivity was less than 2 (Mandal et al, 1998). 

Kang, J. and Ou, Q., Chiral separation of racemic mexilitine hydrochloride using cyclodextrins as chiral additive by capillary electrophoresis,. Chromatogr. A, 795, 394, 1998. 

Commercial LASs are complex mixtures of four individual LASs (C10-C13) with 20 possible positional isomers. Isomeric separation can be achieved by solvophobic association with SDS or host-guest interaction with cyclodextrins. Complete resolution of 19 isomers was achieved using 10 mM phosphate buffer (pH 6.8) containing 40 mM SDS and 30% acetonitrile [4]. LAS isomers in technical products were separated using a-cyclodextrin, but complete resolution of all isomers was not achieved [5]. 

CZE using cyclodextrins (CD) as buffer additives has also been employed for the determination of synthetic dyes in various food products. The synthetic dyes New coccine, Erythrosine, Allura red AC, Tartrazine, Sunset yellow FCF, Brilliant blue FCF, Indigo carmine and Fast green FCF were included in the experiments. Measurements were carried out in a used-silica capillary (47 cm length, 40 cm to the detector, 50 pm i.d.). Capillary temperature was 25°C and separation voltage was 20 kV. Pressure injection was performed... 

Bergholdt, A.B., Jprgensen, K.W., Wendel, L., Lehmaim, S.V. Fast chiral separations using sulfated fS-cyclodextrin and short-end injection in capillary electrophoresis. 

It should be pointed out that capillary GC is more suitable for the separation of some volatile enantiomers in a complex matrix, such as essential oils, where high peak capacity and hence high column efficiency is required [69, 70]. Approximately 50 components including enantionmers in the natural peppermint oil were separated using a GC method [70]. Eight pairs of volatile lactone emantiomers were resolved by GC with a y-cyclodextrin-based column [71]. 

Cyclodextrins are commonly available in three different sizes (i.e., a, /3, -y), and further CD derivatives are now commercially obtainable. Native CDs are often used in CE, since they are not very expensive and numerous compounds are baseline-resolved in chiral separation using CD as buffer additives. /3 -Cyclodextrin interacts with a wide variety of compounds, but... 

YY Rawjee, RL Williams, G Vigh. Capillary electrophoretic chiral separations using /3-cyclodextrin as resolving agent. II. Bases chiral selectivity as a function of pH and the concentration of / -cyclodextrin. J Chromatogr A 652 233-245, 1993. 

A Shibukawa, DK Lloyd, IW Wainer. Simultaneous chiral separation of leu-covorin and its major metabolite 5-methyltetrahydrofolate by capillary electrophoresis using cyclodextrins as chiral selectors. Estimation of the formation constant and mobility of the solute—cyclodextrin complex. Chromatographia 35 419-429, 1993. 

A number of CE/MS applications have been published in the field of chiral separations, mostly using cyclodextrins as chiral selectors. In some cases the partial-filling technique was used (see earlier). The importance of... 

Permethylation of CD hydroxyl groups markedly changes the chromatographic selectivity in comparison to native CDs. Various CD derivatives are described. The various moieties used to functionalize the CDs greatly affect the enantioselectivity. Since the pioneering work of Armstrong, the topic of separations with cyclodextrins or cyclodextrin derivatives has been well documented (44). 

Another commonly used cyclodextrin Capfi oiulfobutylether ofi-CD (SBE-ft-CD), is a polyanionicp-cyclodextrin derivative with a sodium sulfonate salt separated from the lipophilic cavity by a butyl ether spacer group, or sulfobutylether. BotfHBGPand sulfobutylether qf-CD (SBE-p-CD) are widely used cyclodextrins for solubility-enhancing purpose. 

In 1978, Harada et al. [17] used polymerized CD with gel support for the chiral resolution of mandelic acid and its derivatives. Later Zsadon et al. [18-21] used cyclodextrin-based CSPs for the chiral resolution of indole alkaloids, with aqueous buffers as the mobile phases. Today CD-based CSPs have a good reputation. In separate studies, Fujimura [22] and Kawaguchi [23] and their colleagues resolved the enantiomers of aromatic compounds in the reversed-phase mode. Armstrong et al. [29,30,33,34,41,44 46,48,54-63] carried out extensive and remarkable work on the chiral resolution of various racemic compounds using CD-based CSPs. 

A Guide to Using Cyclodextrin Bonded Phases for Liquid Chromatography, Advanced Separation Technologies, Inc., Whippany, NJ (1996). 

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